Many lasers operate as pulsed sources and the pulse duration is determined by the duration of effective pumping, intra-resonator energy extraction rates, etc. However, in certain applications which utilize the pulsed lasers it is advantageous to extend the duration of the pulsed laser beam without reducing the pulse energy. The duration of the pulsed laser beam can be increased by using a laser pulse stretcher which stretches the laser pulses temporally. The stretching or lengthening of the temporal pulse width of the laser beam is done for a wide-variety of reasons and applications. For example, the stretching or lengthening of the temporal pulse width of the laser beam can be done to reduce speckle, reduce the damage on optical components by lowering the peak intensity and lengthening the duration of a single laser pulse that interacts with the optical components, or to optimize the pulse length of the laser pulse for the work on materials which are being irradiated for transformation such as crystallization by sequential layer process or laser ablation.
The traditional laser pulse stretching unit has one or more delay lines which are used to take a single input beam and create multiple beams which are delayed with respect to one another to generate an output beam which is the summation of all of the beams. However, the traditional laser pulse stretching unit can be difficult to reconfigure to change the temporal profile of the output beam for use in another application or to optimize the temporal profile of the output beam for use in the current application. For example, the traditional laser pulse stretching unit may have delay line(s) with refocusing optics that keep the beam from diverging when traveling around the loop(s) of the delay line(s) and these refocusing optics are set for the given length(s) of the delay line(s). Hence, if one wanted to reconfigure this traditional laser pulse stretching unit, then they would have to replace the refocusing optics and this replacement would also require the re-alignment and mechanical changes to the mounting of the delayed line's optics. Accordingly, there is a need to address this shortcoming and other shortcomings associated with the traditional laser pulse stretching units. This need and other needs are satisfied by the present invention.